EP300/YAP1-SERPINE1 Signaling Regulates Ductular Reaction and Liver Fibrosis in Biliary Atresia

Background: Biliary atresia (BA) is the most prevalent cholestatic liver disorder that affects infants. BA is characterized by ductular reaction (DR) and liver fibrosis (LF). The mechanistic basis for DR and LF induction in BA is unknown. In this study, we examined the molecular signals within cholangiocytes that facilitate cell-cell interactions that result in LF.

Methods: The study employed BA liver tissue and cellular models to investigate the expression, localization and function of YAP1 and utilized assay for transposase-accessible chromatin with high-throughput Sequencing (ATAC-seq) and RNA Sequencing (RNA-seq) analyses on rhesus rotavirus (RRV)-infected cholangiocyte organoids (COs) to identify downstream targets of YAP1. Experimental techniques including immune precipitation-mass spectroscopy, co-immune precipitation, chromatin immune precipitation, cleavage under targets and release using nuclease, and dual-luciferase reporter assays were applied to explore transcriptional regulation mechanisms. In vivo validation involved pharmacologic inhibition of EP300 in RRV-induced mouse models and functional assessment of COs derived from BA patients and RRV mice.

Results: YAP1 was upregulated in cholangiocytes of a subset of BA patients and promoted cholangiocyte proliferation while activating hepatic stellate cells in cellular models. SERPINE1 was identified as a potential downstream target of YAP1 through ATAC-seq and RNA-seq analyses. Mechanistically, EP300 acted as a coactivator facilitating SERPINE1 transcription via the YAP1/TEAD binding site within the SERPINE1 promoter. Pharmacologic inhibition of EP300 in RRV mice significantly reduced DR and LF, while improving cholangiocyte permeability and junction integrity in both BA patient-derived and RRV COs.

Conclusion: This study describes an important role of EP300/YAP1-SERPINE1 pathway in the progress of DR associated LF. Also, our results indicate that the suppression of EP300 could be a potential approach for treating progressive LF in patients with BA.

EP300; YAP1; biliary atresia; ductular reaction; liver fibrosis.